Billionaire businessman David Koch is pushing back against reports that he endorsed Wisconsin Governor Scott Walker at a private luncheon held in New York Monday. An aide to the wealthy conservative donor, Mark Short, president of Freedom Partners, a Koch-funded group, said “David was complimentary of Walker but he did not issue an endorsement.”

Walker has, however, benefited from the Koch brothers support in the past. They contributed to his gubernatorial election in 2010 and generously to his recall election in 2012 and his re-election in 2014, spending several million dollars through third party campaign organizations that don’t have to operate under the confines of contribution restrictions.

Koch money is highly coveted in Republican politics. The wealthy entrepreneurs have spent north of $1 billion in helping Republicans get elected and in a potentially crowded presidential primary, to get Koch support would be a financial boon.

Koch support for Walker stems back to at least his 2010 election for governor. The money is difficult to trace because reporting donors is not required, but open governance groups in Wisconsin estimated that one Koch-funded group, Americans for Prosperity, spent about $3.7 million in television advertisements alone that benefited Walker, according to the Wisconsin Democracy Campaign. That doesn't include the money spent on organizing efforts and other activities that AFP in that tangentially helps a candidate.

AFP, which has chapters in 44 states around the country, is highly active in Wisconsin and while it was engaged in Wisconsin prior, it became a prominent player there when Walker gutted collective bargaining for teachers and state employees in 2011, an action that led to his recall election.

After a successful run in Wisconsin, helping to promote Walker’s conservative policies, the head of AFP in Wisconsin at the time, Luke Hilgemann, received a nice promotion and is now the CEO of the groups national organization based in Virginia.

In more traceable political contributions, Koch Industries, the conglomerate owned by Charles and David Koch, was the largest donor to the Republican Governors Association in 2014, giving more than $5 million. In 2012, the year of Walker’s recall election, Koch Industries gave more than $2 million to the group, which spent heavily in Walker’s recall and reelection. Koch Industries also donated $53,000 directly to Walker's campaigns.

The Koch brothers have business interest in Wisconsin employing thousands of people, including an oil pipeline owned by its subsidiary Koch Pipeline Company and refineries operated by another subsidiary Flint Hills Resources. Georgia-Pacific, a paper and wood manufacturing company owned by Koch Industries, is home to numerous offices in the Badger State.

Walker has met with the Koch brothers. He attended a summit in Palm Springs, California earlier this year to meet with Koch donors. It was the same summit that hosted Senators Rand Paul, Ted Cruz and Marco Rubio, potential presidential rivals, but Walker didn’t speak at the portion that was covered by the press. Instead he spoke to donors in a closed door setting.

Walker also received criticism during the union protests for taking a phone call from David Koch. The call was leaked to the press because the caller ended up being a prank. In his book "Unintimidated," Walker said his conversation with the prankster was proof that he had never spoken to Koch before because he didn’t know that it was not his voice. But Walker told the caller, whom he thought was Koch, “Thanks, thanks for all the support and helping us move the cause forward, and we appreciate it.”

At the luncheon in New York Monday, an attendee in the room said Koch told the audience, “My brother and I are going to take a neutral position as to who we are going to support until the primaries are over by the beginning of..... in the summer of next year...so when the primaries are over and Scott Walker gets the nomination, well then we will support." The audience laughed.

Walker also attended the audience at the luncheon, which was hosted by the New York Republican Party, and the comments were made after Walker had left.

While Koch told the audience that he wasn’t getting involved in the primaries, the question appears to still be up in the air. Short, president of Freedom Partners, said the Koch brothers declined to say if the Koch brothers will become involved in the Republican primaries, but acknowledged that it’s too early in the presidential nominating process to determine how to get involved.

“That’s not taking it off the table but it’s also not announcing intentions to get engaged,” Short said.

Leigh Ann Caldwell

Leigh Ann Caldwell is a political reporter for NBC News who covers Capitol Hill and elections.